President Obama announced Tuesday that 7.1 million Americans have signed up for health plans under the Affordable Care Act, the most ambitious federal effort in nearly half a century to widen access to coverage.

The tally, which signified a sharp turnaround from the troubled beginnings of enrollment last fall, was driven upward by a late rush of consumers seeking coverage in the days and hours before the deadline of midnight Monday to select health plans for 2014.

Even after the official cutoff, more than 100,000 people at a time were on HealthCare.gov, the online federal insurance marketplace, into the early morning hours, according to a person familiar with the details of the last-minute surge. People who have started to enroll on the federal exchange, as well as on some state exchanges, have a grace period to finish their applications.

“This law is doing what’s it’s supposed to do,” a buoyant Obama said in late-afternoon remarks in the White House Rose Garden. “It’s working. It’s helping people from coast to coast.”

The 7.1 million total means that the six-month sign-up period achieved results that congressional budget analysts had first anticipated — and more recently had thought would be impossible. Two months ago, the analysts downgraded their forecast from 7 million to 6 million, taking into account massive computer trouble with HealthCare.gov for much of the fall that frustrated many people trying to shop for health plans.

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The tally is based on the number of people who enrolled for coverage by Monday’s deadline through the new federal insurance marketplace operating in three dozen states. It also includes people who enrolled in 14 state-run marketplaces as of the deadline or, in the case of a few states, by last weekend.

As surprise about the high total rippled among the Obama administration’s friends and foes alike, they agreed that the law had met the threshold test of whether it could attract large numbers to federal and state-run insurance marketplaces.

The last-minute enrollment had several causes: Eagerness by some people to gain affordable health benefits. Wariness of running afoul of the first federal law requiring most Americans to be insured. Campaign-like techniques that the administration employed, especially since January, to urge people to sign up.

“It’s an amazing achievement,” said Chris Jennings, who helped direct the White House’s implementation of the law until he returned to the private sector a few months ago.

Republicans, who have not relinquished their crusade to dismantle the 2010 legislation, were praising but more skeptical. “At some level you have to take your hat off and say congratulations,” said Douglas Holtz-Eakin, president of the American Action Forum and a former director of the Congressional Budget Office. But he was quick to add, “It’s an interim accomplishment at best.”

Health policy experts said that the long-term significance of the high enrollment numbers for this first year of insurance will take time to clarify. “There is still a lot of haze around this,” said Jonathan Oberlander, a professor at the University of North Carolina at Chapel Hill who studies health-care politics.

Oberlander and others noted that the number of people who have gotten coverage varies significantly by state. In addition, uncertainty lingers about how many people who have signed up have actually begun to pay for their new health plans, how many will continue to pay for them, and how many of the enrollees had no insurance before.

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Even in what was essentially a victory announcement, Obama sounded cognizant of the political minefield still surrounding the law, presenting anew a justification for its existence. “But the bottom line is this: Under this law, the share of Americans with insurance is up and the growth of health-care costs is down, and that’s good for our middle class and that’s good for our fiscal future,” he said, with Vice President Biden at his side. “And there’s no good reason to go back.”

Senior administration officials said the fact that a large number of Americans signed up by the deadline will make it easier to defend the law on the campaign trail this year.

Several Democratic senators are running for reelection in states where the GOP is trying to fan opposition to the law. One of the most vulnerable, Sen. Mary Landrieu (La.), hailed Tuesday’s news. “Today’s enrollment announcement confirms what I have said since day one — the Affordable Care Act holds great promise and is getting stronger every day,” she said in a statement.

The late enrollment boom suggests that the administration’s outreach effort was effective, even though it started essentially two months late while problems with HealthCare.gov were being worked on. Officials relied on many of the same campaign tactics, including social media and regional talk radio, that Obama’s aides used two years ago — this time, their goal was to bring young people, Latinos and African Americans into the nation’s health-care system.

The administration worked closely with allied groups — including Enroll America, the Service Employees International Union and Planned Parenthood — to sign up consumers in 25 cities, including Atlanta, Dallas and Miami, that have high numbers of uninsured and are in states that relied on the federal exchange instead of creating their own.

Just as people rushed to the federal health insurance exchange Monday, states faced their own deluge. Web page views on California’s health exchange were four times as many as its second-busiest day. Like the federal government, California and a few other states are giving those who started the process extra time to pick a plan.

Amy Goldstein is a national reporter for The Washington Post focused on health-care policy.

Juliet Eilperin is The Washington Post's White House bureau chief, covering domestic and foreign policy as well as the culture of 1600 Pennsylvania Avenue. She is the author of two books—one on sharks, and another on Congress, not to be confused with each other—and has worked for the Post since 1998.

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